Correlation between the densities of X-ray sources and interstellar gas     

M. Fujimoto  S. Hayakawa  T. Kato 《Astrophysics and Space Science》1969,4(1):64-83

The distribution of X-ray sources in our galaxy is obtained, assuming that the absolute X-ray luminosities of these sources are the same. The distribution is found to be in good correlation with the distribution of interstellar gas. The density of X-ray sources is nearly proportional to the square density of gas. This indicates that X-ray sources are comparatively young. The relation between the densities of X-ray sources and gas allows us to estimate the X-ray intensities of various objects such as Magellanic Clouds and Andromeda nebula, and also to obtain the average X-ray luminosity of spiral galaxies. The latter should increase as the age of a galaxy decreases, since the amount of gas decreases as the galaxy evolves. Under the assumptions that the gas density is inversely proportional to the age and that galaxies older thant ₀/30 are visible in X-rays, wheret ₀ is the present age of the universe, the contribution of X-ray sources in distant galaxies to the background component is calculated. The intensity and the spectrum of the background component of X-rays thus obtained are in fair agreement with observed ones in the energy range between 1 and 4 keV but significantly deviate from the latter at high energies.  相似文献   

Geochemical characteristics of crude oils from the Sagara oil field, Shizuoka Prefecture, Japan     

Susumu  Kato  Amane  Waseda  Hideki  Nishita 《Island Arc》2006,15(3):304-312

Abstract   Six oil samples collected from the Sagara oil field, Shizuoka Prefecture, were geochemically analyzed. Unlike the Niigata oils, the Sagara oils: (i) are low-sulphur light oils dominated by gasoline and kerosene fractions; (ii) have low values of environment index in light hydrocarbon compositions; (iii) have high Pr/ n -C₁₇ and low Ph/ n -C₁₈ ratios and high oleanane/hopane ratios; (iv) have high relative abundance of C₂₉ and low relative abundance of C₂₈ regular steranes; and (v) have 'light' stable carbon isotope compositions. These characteristics show that the source rocks of the Sagara oils contain mainly marine organic matter, but with more input of terrigenous organic matter deposited under more oxic conditions compared to those of the Niigata oils. The light carbon isotope compositions and the low relative abundance of C₂₈ regular steranes of the Sagara oils suggest that their source rock is not Miocene, but probably Paleogene in age. The Sagara oils probably migrated along faults from deeper parts of the basin.  相似文献   

The SOLAR-A mission: An overview     

Y. Ogawara  T. Takano  T. Kato  T. Kosugi  S. Tsuneta  T. Watanabe  I. Kondo  Y. Uchida 《Solar physics》1991,136(1):1-16

The SOLAR-A spacecraft is to be launched by the Institute of Space and Astronautical Science, Japan (ISAS) in August, 1991. As a successor of HINOTORI, this mission is dedicated principally to the study of solar flares, especially of high-energy phenomena observed in the X- and gamma-ray ranges. The SOLAR-A will be the unique space solar observatory during the current activity maximum period (1989–1992). With a coordinated set of instruments including hard X-ray and soft X-ray imaging telescopes as well as spectrometers with advanced capabilities, it will reveal many new aspects of flares and help better understand their physics, supporting international collaborations with ground-based observatories as well as theoretical investigations. An overview of this mission, including the satellite, its scientific instruments, and its operation, is given in this paper. Also the scientific objectives are briefly discussed.After the launch the name of SOLAR-A has been changed to YOHKOH.  相似文献   

The solar differential rotation and ‘Rossby-type’ waves     

Shoji Kato  Y. Nakagawa 《Solar physics》1969,10(2):476-493

It has been suggested that the solar differential rotation might be maintained by nearly horizontal non-spherical convective circulation called the Rossby-type waves (the wave motions characterized by the close balance of the Coriolis force and pressure gradient in horizontal motions). In this paper, such Rossby-type waves which could be excited in the upper solar convection zone are considered, and the possibility of maintenance of the solar differential rotation by such waves is examined. A numerical estimate, in terms of the rate of conversion of the kinetic energy of such wave motions into the mean rotational motion, indicates this possibility. The implications and limitations of the results are also discussed.Visiting Scientist to the High Altitude Observatory on leave of absence from the Department of Astronomy, University of Tokyo, Japan.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

State of stress within a thin elastic wedge: a model of internal deformation of the continental plate at arc—arc junctions     

Teruyuki Kato  Kunihiko Shimazaki  Ken'ichiro Yamashina 《Geophysical Journal International》1980,60(3):377-390

Summary. Anomalous stress distributions near arc—arc junctions have been found in several parts of the world. As a simple two-dimensional model, a thin elastic wedge is introduced to model the continental side of the arc—arc junction, and the stress distribution within it is calculated to interpret those anomalies. Uniform normal and/or shear stress boundary conditions are given separately to each edge to approximate the effect of the two neighbouring converging plate boundaries; Stress components are obtained by numerical integration. Among the various results, the following features are predominant and seem to be actually taking place at arc—arc junctions.
(1) The anomaly in stress pattern within the wedge is basically due to the difference in stress conditions between the two boundaries.
(2) A large stress concentration takes place when symmetrical shear stresses are applied to the two edges.  相似文献   

On interpolation functions in traveltime tomography     

Masatoshi Miyazawa  Mamoru Kato 《Geophysical Journal International》2004,158(1):169-178

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A new approach to time-dependent inversion of geodetic data using a Monte Carlo mixture Kalman filter   总被引：1，自引：0，他引：1  

Jun'ichi Fukuda  Tomoyuki Higuchi  Shin'ichi Miyazaki  Teruyuki Kato 《Geophysical Journal International》2004,159(1):17-39

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Atmospheric Corrections Using MODTRAN for TOA and Surface BRDF Characteristics from High Resolution Spectroradiometric/Angular Measurements from a Helicopter Platform     

Yaping Zhou  Ken C. Rutledge  Thomas P. Charlock  Norman G. Loe  Seiji Kato 《大气科学进展》2001,18(5):984-1004

High-resolution spectral radiance measurements were taken by a spectral radiometer on board a heli copter over the US Oklahoma Southern Great Plain near the Atmospheric Radiation Measurements (ARM) site during August 1998. The radiometer has a spectral range from 350 nm to 2500 nm at 1 nm resolution. The measurements covered several grass and cropland scene types at multiple solar zenith angles. Detailed atmospheric corrections using the Moderate Resolution Transmittance (MODTRAN) radiation model and in-situ sounding and aerosol measurements have been applied to the helicopter measurements in order to re trieve the surface and top of atmosphere (TOA) Bidirectional Reflectance Distribution Function (BRDF) characteristics. The atmospheric corrections are most significant in the visible wavelengths and in the strong water vapor absorption wavelengths in the near infrared region. Adjusting the BRDF to TOA requires a larger correction in the visible channels since Rayleigh scattering contributes significantly to the TOA reflectance. The opposite corrections to the visible and near infrarred wavelengths can alter the radiance dif ference and ratio that many remote sensing techniques are based on, such as the normalized difference vege tation index (NDVI). The data show that surface BRDFs and spectral albedos are highly sensitive to the veg etation type and solar zenith angle while BRDF at TOA depends more on atmospheric conditions and the vi ewing geometry. Comparison with the Clouds and the Earth＇s Radiant Energy System (CERES) derived clear sky Angular Distribution Model (ADM) for crop and grass scene type shows a standard deviation of 0.08 in broadband anisotropic function at 25° solar zenith angle and 0.15 at 50° solar zenith angle, respectively.  相似文献   

METEOROLOGICAL CHARACTERISTICS DURING THE SECOND MEIYU EPISODE IN 1998     

张雁  马强  加藤内藏进 《Acta Meteorologica Sinica》2002,(3)

This article examined the meteorological features of the second Meiyu/Baiu episode(hereafterMeiyu Ⅱ)in 1998 and the results are summarized as follows:(1)The Meiyu Ⅱ period in 1998 hasbeen the longest and the most delayed ending one since 1885,which caused the great flood aroundthe Yangtze River Basin.The circulation situation in Meiyu Ⅱ is so typical that the averagegeopotential height and wind fields at 500 hPa and 850 hPa are very similar to monthly mean inJune.The abnormal circulation in Meiyu Ⅱ is associated with an adjusting of the Okhotsk high andshort period south-north oscillation of the subtropical high.(2)The heavy rainfall around theYangtze River during Meiyu Ⅱ period is closely related to a persistent shear line,a clear eastwardmoving vortex structure and a very strong jet flow at lower levels.It is very clear that the strongdivergence at higher levels and convergence at lower levels occurred in situ during Meiyu Ⅱ period.(3)It is very clear that the convective activity propagates eastward quickly with a period about 7days during Meiyu Ⅱ period.  相似文献   

Has the plate boundary shifted from central Hokkaido to the eastern part of the Sea of Japan?     

Naoko Kato  Hiroshi Sato  Masayuki Orito  Kazuomi Hirakawa  Yasutaka Ikeda  Tanio Ito   《Tectonophysics》2004,388(1-4):75

A NS trending Cenozoic fold-and-thrust belt has developed in the western part of the Hidaka Collision Zone (HCZ), central Hokkaido, Japan. A quantitative estimation of the late Cenozoic convergence rate at the front of the Hidaka thrust system is important in revealing the plate tectonic framework around northern Japan. High-resolution seismic reflection profiling across the active fault-related folds was carried out to ascertain the temporal change in the crustal shortening rate. Overlapping ramp anticlines and growth folds within thrust sheets were examined using balanced cross-sections combined with industry seismic and drilling data. The rate of shortening was examined using a 3.5 Ma horizon and late Quaternary horizons at 115 and 41 ka. These horizons show that the convergence rate of the Hidaka thrust system has not decreased during the last 3.5 Ma. This suggests that the plate boundary between the Eurasian (Amurian) and North American (Okhotsk) plates has not jumped from the central part of Hokkaido to the eastern part of the Sea of Japan since 3.5 Ma and that a significant amount of plate convergence is still being absorbed in the Hidaka Collision Zone.  相似文献